1. Field of the Invention
The present invention relates to pneumatic stamping devices and, in particular, to an apparatus which is pneumatically operated and effective to approach and stamp a hot metallic object with an identifying impression.
2. Description of the Prior Art
A perenninal problem attendant in various industries is the individual identification of objects. Such objects may include metals or wood products and may be of a large physical size. An example of the types of concerns involved with the identification of such objects arises in relation to the steel industry. In that environment, some means must be provided for the indentification of large steel products such as billets, blooms, slabs or the like. The practice of stamping identifying markings into the surface of such objects to a depth of 0.015 to 0.030 inches has developed in response to those needs. While the stamping of identifying information on such objects is feasible, it will be readily appreciated that it is advantageous to stamp the material immediately after forming and, therefore, while very hot, due to the reduced strength of the steel while at an elevated temperature. However, due to the extreme temperature of the steel immediately after it has undergone forming operations, it is dangerous and impractical for a worker to approach the steel to manually stamp the identifying information thereon.
For this reason, mechanized devices for accomplishing the stamping of materials such as steel billets have been developed. However, for various reasons, including those set forth hereinbelow, all previous identification stamping mechanisms have serious problems associated therewith which have heretofore been unsolvable.
One example of a prior art stamping apparatus which is fairly indicative of the state of the art includes a piston which is free moving within a cylinder. Upon activation of a trigger rod which controls a valve means, the piston is propelled along the cylinder by means of compressed air and is caused to indirectly strike type characters which, in turn, strike the object to be marked leaving identifying symbols idented thereon.
In particular, an early generation model of such a stamping device included a source of compressed air in communication with the cylinder in the area behind the piston. The introduction of the compressed air behind the piston was controlled by a complicated valve means which provided a tortuous route for the air to traverse which valve means included the extended trigger rod which extended to the leading end of the cylinder. Mounted on the front end of the cylinder was a slidable housing which accepted a plunger in engagement with an anvil. A cartridge containing the type characters was supported by the housing at the leading end thereof. A support which enabled the manual displacement of the device into proximity with the object to the stamped, such as a jib or a track configuration, was also provided.
To utilize such a stamping device it was manually swung or pushed into contact with the object to be marked. Such contact would displace the slidable housing into contact with the elongated trigger rod. The displacement of the trigger rod would cause the actuation of the valve means which would allow compressed air to pass through the valve means and enter the cylinder behind the piston. The piston would then be driven along the length of the cylinder and strike the plunger thereby, respectively, driving the plunger into the anvil, and the type mounted in the cartridge into the object.
As is known by those skilled in the art, such a device as described immediately above suffered from a host of serious problems. First, by the manual thrusting of the stamping device into contact with the object to be stamped, the stamping device would be caused to bounce back from the object for a time period before the trigger rod could activate the valve, the compressed air could traverse its tortuous route and the piston could travel down the cylinder striking the anvil and causing the type to strike the object. Such an initial striking of the object with the type and the bouncing back therefrom accompanied by the delay before the principal impact of the type therewith caused a double, skewed indentation on the object often rendering the marking illegible. In addition, such bouncing removed the stamping device from immediate proximity with the object thereby decreasing the effectiveness of the stamping because the type had a greater distance to travel and would not achieve its proper indentation depth.
One attempt to rectify certain of the shortcomings of the above-discussed prior stamping device included the provision of an air cylinder parallel to and connected by means of a keel-shaped bracket to the stamping device in order to mechanically move it into proximity with the object to be stamped rather than by means of the jib or track. However, such a configuration was frought with difficulties of its own. For example, due to the moment arm created in the keel-shaped bracket between the axis of the stamping device and that of the transport air cylinder, upon impact with the object, deflection would occur in the system thereby causing chatter and undesirably distorting the stamping indentation.
In an attempt to alleviate certain of the shortcomings of the prior stamping devices yet another device was developed. In that apparatus, the entire stamping device assembly was mounted into a hollow piston rod of a large diameter air cylinder. When the piston rod of the large air cylinder was extended, the stamping device would be brought into contact with the object. In the manner of the prior generation devices, the head of the stamping device would contact the object thereby displacing the head which would, in turn, displace the trigger rod. The displacement of the trigger rod would activate the valve means allowing air to enter the cylinder behind the piston after the compressed air traversed its complicated route to drive the piston into indirect contact with the stamping characters.
It has become apparent that problems still exist with stamping devices such as those most recently described. Due to the mechanical linkage between the trigger rod and the valve means, a certain time lag is present in such a device between the time of head contact with the object and the time of the stamping impact. Also, due to the design of the valve mechanism creating the tortuous route for the compressed air and its reliance on the trigger rod, additional delays are present. From above, such delays are problematic in that they have been found to cause chatter between the stamping type and the workpiece thereby destroying the stamping image. Further, such a system has grown overly complicated for its intended function and, hence, is difficult and costly to manufacture and to maintain.
The subject invention is directed toward an improved pneumatic stamping apparatus which overcomes, among others, the above-discussed problems and provides a cost-effecient pneumatic stamping apparatus which is effective to consistently produce a clear image on an article to be identifyingly stamped.